A variety of seat track designs have been proposed to meet the growing demand for a seat track system that permits comfort adjustment of the seat, and permits the seat to slide forward to provide access to the rear of the seat "remembering" its initial position and then returns and locks in that "remembered" position.
However, the designs are mechanically complex in their operation, prone to manufacturing difficulties when produced in "high volume" production, costly to produce and subject to failure due to in service wear and tear and poor design.
In practice, it has been found that a common weakness of these designs is related to the mandatory requirement that the memory system be very rapid in its operation in order that the locking mechanism cannot skip over the "remembered" position when the seat is forcefully returned to the desired preset driving position. As will be known by those skilled in the art, current safety standards require such seating systems withstand a minimum forward pull test in the order of 5,000 pounds force. This mandates robust construction and the attendant inertia mass, thus requiring the use of powerful springs to cause rapid actuation of the mechanism, making it difficult to operate the system smoothly. See for example, United Kingdom patent application Nos. 2,033,738; 2,091,548; and 1,459,605 and U.S. Pat. No. 3,940,182 and 4,101,169.
In some of those references, "memory devices" are provided which purport to mechanically "remember" the initial position of the seat when the seat is released from its locked position and is moved forward to permit access behind the seat.
Other approaches are shown in U.S. Pat. No. 4,440,442 and United Kingdom Pat. No. 1,344,271.
U.S. Pat. No. 4,440,442 does not provide a true memory as such which sets itself when the seat slides forward. Rather this Patent teaches the use of upper and lower vertically stacked track assemblies slideable relative to one another only one of which moves at one time and provides minimal adjustment and access.
United Kingdom Pat. No. 1,344,271 discloses a vertically upstanding tab moveable along a track and lockable with respect thereto and a slide to which the seat is secured slideable along the track and carrying a pivotable clasp comprising an aperture therethrough to capture and hold the tab through the aperture in the clasp until the clasp is lifted by rotation caused by the pivoting of the seatback freeing the tab to permit relative movement of the slide relative to the track and tab.
However, this proposal suffers many deficiencies. When the tab is released (freed) from the clasp, the seat can move either forward or backward. Additionally, the clasp-tab arrangement does not provide a positive secure lock arrangement and is easily dislodged. In a rear-end collision, the clasp could be dislodged and the seat easily thrown to the back of the vehicle.
Another serious deficiency of the system proposed by United Kingdom Pat. No. 1,344,271 relates to its inapplicability to curved seat track systems. Many seat track systems presently manufactured, provide for a curved track and curved slide for carrying the seat for movement along the track. The curve usually extends from a raised position closer the windshield to a lower position further from the windshield to position the eyes of both taller and shorter drivers at the same horizontal level. As a short driver would normally sit closer to the windshield, he is positioned at a higher level, whereas a taller person having longer legs and a longer torso is positioned to sit further from the windshield and at a lower level.
It is therefore an object of this invention to provide a comfort adjustment manual override seat track assembly for use with a seat which is easy to manufacture, entirely reliable, mass produceable at minimal cost and applicable to curved track systems.
Further and other objects of the invention will be realized by those skilled in the art from the following summary of the invention and detailed description thereof.